1. Field of the Invention
The field of the invention relates to security inspection systems generally, and more particularly, to a passenger inspection system that can detect weapons proximate a passenger's feet and/or leg(s).
2. Discussion of Related Art
Extant security inspection systems use known technologies such as nuclear magnetic resonance (NMR), nuclear quadrupolar resonance (NQR), metal detection, and x-rays, among others, to detect weapons, explosives, illegal drugs, and other kinds of substances of interest in and/or on an item, such as shoes, luggage, clothing, and the like.
When security is heightened, persons to be scanned are often required to remove their shoes. The shoes are then typically placed in plastic tubs that move, via a conveyor belt, into an x-ray scanner. Additionally, or alternatively, security personnel may visually inspect the shoes, swab the interior and/or exterior of the shoes for trace detection purposes, and/or pass a hand-held metal detector over the shoes. Such methods consume time, inconvenience passengers, and slow the rate of a security checkpoint's throughput. A need therefore exists for a solution that enables simple and accurate detection of weapons, explosives, drugs, and/or other substances of interest that may be hidden in a person's shoes while the shoes are being worn. Another need exists for a solution that provides simple and accurate detection of weapons, explosives, illegal drugs, and/or other substances of interest that may be hidden, alternatively or additionally, in the person's socks and/or clothing present on the person's leg(s) while such socks and/or clothing are being worn.
Various devices have been developed in attempts to provide solutions to one or more of these needs. One example of such a device is a walkthrough quadrupole resonance (“QR”) shoe scanner that positions a QR sensor in the floor of the shoe scanner and flanks the QR sensor with two opposing vertical side walls that are electrically connected to the floor of the shoe scanner. A channel formed by the space between the opposing vertical side walls extends the length of the shoe scanner so that a person can enter one (open) end of the shoe scanner and exit the opposite (open) end. As the person stands in the central portion of the QR shoe scanner, the QR sensor operates to detect alarm objects (e.g., weapons, explosives, illegal drugs, etc.) in or on the person's shoes, socks, or articles of clothing.
Another example is a passenger screening system that positions a QR sensor in a floor of the passenger screening system and flanks the QR sensor with three vertical, electrically conductive walls that are joined together and attached to the floor of the passenger screening system. The three vertical, electrically conductive walls include two electrically conductive and opposing side walls and one electrically conductive end wall. A channel formed by the space between the opposing side walls extends from an open end of the passenger screening system to the end wall that forms the opposite end of the passenger screening system so that a person can enter and exit the passenger screening system only from the open end of the channel. The passenger screening system also includes a metal detection sensor having two metal detector conductive traces—a first metal detector conductive trace positioned on one of the opposing side walls; and a second metal detector conductive trace positioned on the other of the opposing side walls.
The metal detector conductive traces are configured to generate a uniform magnetic field when no metallic object or substance is present within the scanning area. Any metallic object or substance that is later positioned within the scanning area will disturb the otherwise balanced magnetic field generated by the metal detection conductive traces. This disturbance creates an electrical and/or magnetic imbalance between the metal detector conductive traces, which causes the passenger screening system to receive a signal indicating that a metallic object has been detected within the scanning area.
It would further be advantageous to provide an improved metal detector apparatus and method configured to detect weapons concealed proximate a person's shoes, and/or configured to detect weapons proximate the person's leg(s).